Transdermal absorption sheet, and manufacturing method for the same

ABSTRACT

A transdermal absorption sheet and a manufacturing method for the transdermal absorption sheet includes a laminating step of forming a multilayer film with a viscosity difference by forming, on a support, a lower layer containing a first transdermal absorption material and an upper layer containing a drug and a second transdermal absorption material and having a lower viscosity than the lower layer, a filling step of filling needle-like recessed portions corresponding to inverted needle-like protruding portions with a solution of the transdermal absorption material by pressing a mold in which the needle-like recessed portions are arranged in a two-dimensional array, against a surface of the multilayer film supported by the support to allow the multilayer film to flow, a solidifying step of solidifying the multilayer film with the mold pressed against the surface of the multilayer film, and a peeling-off step of peeling the solidified multilayer film from the mold.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT International Application No.PCT/JP2013/080538 filed on Nov. 12, 2013, which claims priority under 35U.S.C. §119(a) to Japanese Patent Application No. 2012-249678 filed onNov. 13, 2012. Each of the above application(s) is hereby expresslyincorporated by reference, in its entirety, into the presentapplication.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a transdermal absorption sheet and amethod for manufacturing the transdermal absorption sheet and inparticular, to a technique for concentrating a drug at microneedles.

Description of the Related Art

Conventionally, methods for administering a medicine (drug) or the likethrough a biological surface, that is, the skin or mucosa mostly involveattaching mainly an aqueous material or a powdery material. However,since an attachment area for these materials is limited to the surfaceof the skin, perspiration, contact with foreign matter, or the like maycause the attached medicine or the like to be removed, and administeringan appropriate amount of medicine is difficult. Furthermore, in allowingthe medicine to permeate deep through the skin, it is difficult toreliably control a depth of penetration using a method that utilizespermeation by diffusion of a medicine as described above. Thus,obtaining sufficient drug efficacy has been difficult.

Because of such a situation, a method has been carried out in which atransdermal absorption sheet provided with microneedles (needle-likeprotruding portions) having a high aspect ratio and containing a drug isused to inject a medicine through the microneedles inserted into theskin. In order to make the transdermal absorption sheet available, thedrug needs to be mixed into the transdermal absorption sheet. However,drugs are expensive in many cases, and thus, the drug needs to becontained in the transdermal absorption sheet so as to concentrate atthe microneedles.

A method for manufacturing a transdermal absorption sheet is describedin, for example, Japanese Patent Laid-Open No. 2010-69253 (PatentLiterature 1) and Japanese Patent Laid-Open No. 2008-194288 (PatentLiterature 2).

Patent Literature 1 discloses a manufacturing method for a transdermalabsorption sheet which involves feeding and solidifying a materialsolution containing a drug in a mold in which inverted shapes ofmicroneedles are formed and then feeding and solidifying a materialsolution containing no drug in the mold. According to Patent Literature1, this allows the drug to efficiently concentrate at the microneedle.

Patent Literature 2 is not a technique for efficiently concentrating thedrug at the microneedles but is a technique for improving sustainedrelease of the drug. According to Patent Literature 2, needle-likecomponents are manufactured as follows. That is, Patent Literature 2discloses a method for manufacturing needle-like components by applyingan easily decomposable material to a substrate, then selectivelyapplying a projecting portion material only to a portion correspondingto needle-like recessed portions of the mold or applying the projectingportion material all over the mold to obtain a coating layer, thenpressing a recessed plate provided with inverted shapes of needle-likeprotruding portions against the coating layer, and thereafter peelingthe recessed plate off from the substrate. According to PatentLiterature 2, this enables transdermal administration with sustainedrelease and needle-like components with a sufficient mechanical strengthcan be manufactured.

SUMMARY OF THE INVENTION

However, in the manufacturing method in Patent Literature 1, in thefilling step of filling the mold with the material solution, the fillingis performed in two steps of: filling the mold with the materialsolution containing the drug; and filling the mold with the materialsolution containing no drug. Thus, the method may include an increasednumber of manufacturing steps and have degraded production efficiency.

On the other hand, the manufacturing method in Patent Literature 2 needsa single filling step and has improved production efficiency compared tothe manufacturing method in Patent Literature 1. However, themanufacturing method in Patent Literature 2 is disadvantageous in that,since the projecting portion material is selectively applied to microareas each having a size of approximately 300 μm (a general value forthe inlet diameter of a needle-like recessed portion) corresponding toneedle-like recessed portions two-dimensionally arranged in the mold,the application is a complicated and time-consuming step. Furthermore,when the projecting portion material is applied all over the mold, thecomplicatedness of the application can be avoided, but the needle-likerecessed portions cannot be filled with the projecting portion materialin a concentrated manner. That is, it is difficult to achieveconcentration of the drug at the microneedles, which is a problem to besolved by the present invention, simply by applying the technique inPatent Literature 2.

The present invention has been developed in view of these circumstances.The present invention aims to provide a transdermal absorption sheet anda manufacturing method for the transdermal absorption sheet that allowthe drug to concentrate at the microneedles, while serving to improveproduction efficiency.

In order to accomplish the object, an aspect of the present inventionprovides a manufacturing method for a transdermal absorption sheet inwhich a plurality of fine needle-like protruding portions are arrangedin a two-dimensional array on a surface of a sheet portion supported bya support, the method comprising: a laminating step of forming, on thesupport, a multilayer film which comprises a plurality of layerscontaining a transdermal absorption material, wherein the plurality oflayers satisfy V1>V2≧ . . . ≧Vn≧ . . . ≧Vt when a lowermost layer isrepresented as a first layer, an uppermost layer is represented as at-th layer (t≧2) and a viscosity of an n-th layer is represented as Vn,wherein at least one layer other than the lowermost layer contains adrug; a filling step of pressing a mold in which needle-like recessedportions corresponding to inverted needle-like protruding portions arearranged in a two-dimensional array, against a surface of the multilayerfilm supported by the support to allow the multilayer film to flow andfilling the needle-like recessed portions with a solution of thetransdermal absorption material; a solidifying step of solidifying themultilayer film in a state where the mold is pressed against the surfaceof the multilayer film; and a peeling-off step of peeling the solidifiedmultilayer film from the mold.

According to an aspect of the present invention, in the laminating step,on the support, the multilayer film is formed which has the plurality oflayers containing the transdermal absorption material. In the multilayerfilm, when the lowermost layer is represented as the first layer, theuppermost layer is represented as the t-th layer (t≧2), and theviscosity of the n-th layer is represented as Vn, V1>V2≧ . . . ≧Vn≧ . .. ≧Vt is satisfied, and at least one layer other than the lowermostlayer contains the drug.

In view of production efficiency, preferably t=2 or 3, and morepreferably t=2.

Moreover, in the filling step, a mold in which needle-like recessedportions corresponding to inverted needle-like protruding portions arearranged in a two-dimensional array, is pressed against a surface of themultilayer film supported by the support to allow the multilayer film toflow, thereby filling the needle-like recessed portions with a solutionof the transdermal absorption material.

In this filling step, since the viscosity of layers in the laminatedmultilayer film becomes lower in higher layers, when the mold is pressedagainst the surface of the multilayer film, firstly, the transdermalabsorption material solution in the t-th layer with the lowest viscosityflows into the needle-like recessed portions. Thus, only the transdermalabsorption material solution in the t-th layer with the lowest viscosityis filled into the needle-like recessed portions of the mold.

When the mold is further pressed against the surface of the multilayerfilm, the transdermal absorption material solution in the (t−1)-th layerwith a next higher viscosity than the t-th layer acts to flow into theneedle-like recessed portions. Thus, the transdermal absorption materialsolution in the t-th layer having already reached the middle of each ofthe needle-like recessed portions is pushed toward a tip side of theneedle-like recessed portion. By repeating this process, finally, thetransdermal absorption material solution in the first layer with thehighest viscosity is filled into the needle-like recessed portions.Consequently, the drug can be concentrated at the needle-like protrudingportions in the molded transdermal absorption sheet.

Moreover, in the solidifying step, the multilayer film is solidified ina state where the mold is pressed against the surface of the multilayerfilm. Consequently, even when the filled transdermal absorption materialsolution is solidified and contracted in the needle-like recessedportions, the transdermal absorption material solution is pressed towardthe tip side of each needle-like recessed portion by a pressing force.Thus, the shape of the needle-like recessed portion can be accuratelytransferred. Moreover, in the present invention, the filling iscompleted in one single filling step, leading to improved productionefficiency.

In many cases, a drug to be used has the risk of being thermallydecomposed, and thus, the laminating step, the filling step, and thepeeling-off step of the present invention are preferably executed atnormal temperature. Furthermore, also when the solidifying step isexecuted by means of drying, drying temperature is preferably low enoughto prevent the drug from being decomposed.

In an aspect of the present invention, a viscosity of the lowermostlayer is preferably at least twice as high as a viscosity of theuppermost layer, more preferably at least five times as high as theviscosity of the uppermost layer, particularly preferably at least 10times as high as the viscosity of the uppermost layer, and mostpreferably at least 20 times as high as the viscosity of the uppermostlayer. In order to achieve both the coatability (coating property) andflowability of the uppermost layer and the lowermost layer, theviscosity of the lowermost layer is preferably at most 1,000 times ashigh as the viscosity of the uppermost layer.

When the viscosity of the lowermost layer is at least twice as high asthe viscosity of the uppermost layer, it is possible to increase a timedifference between the start of flow of the transdermal absorptionmaterial solution in the uppermost layer and the start of flow of thetransdermal absorption material solution in the lowermost layer. Thisallows the needle-like recessed portions to be filled with thetransdermal absorption material solution in the uppermost layer in aconcentrated manner. In this case, the viscosity of the uppermost layeris preferably 2 to 30 Pa·s.

Thus, the drug can further be concentrated at the microneedles.

In the present invention, an inlet portion of each needle-like recessedportion in the mold preferably has a tapered portion with a taperedshape.

Thus, when the mold is pressed against the surface of the multilayerfilm to allow the transdermal absorption material solution in theuppermost layer to flow, the transdermal absorption material solution inthe uppermost layer collects in the tapered portion. Consequently, thetransdermal absorption material solution in the uppermost layer can beeasily filled into the needle-like recessed portion. This also appliesto other transdermal absorption material solutions.

In an aspect of the present invention, preferably, a bottom surface ofeach tapered portion is formed into a hexagon, and the needle-likerecessed portions with the tapered portions are arranged so as to form ahoneycomb structure.

Thus, the adjacent needle-like recessed portions are easily evenlyfilled with the transdermal absorption material by a pressure thatpresses the mold against the surface of the multilayer film.

In an aspect of the present invention, preferably, the pressing surfaceof the mold is provided with enclosing members that evenly partition thearea of the multilayer film to be fed into the adjacent needle-likerecessed portions into areas so that the enclosing members protrude fromthe pressing surface.

Thus, when the mold is pressed against the surface of the multilayerfilm, a filling amount of transdermal absorption material solution isaccurately evenly distributed to the individual needle-like recessedportions. Consequently, a possible variation among the plurality ofmolded needle-like recessed portions can be prevented.

Furthermore, particularly preferably, the enclosing members and thetapered portions arranged in a honeycomb shape are combined together.

In an aspect of the present invention, preferably, an air vent hole isformed at a tip of the needle-like recessed portion. This allows each ofthe needle-like recessed portions to be easily filled with thetransdermal absorption material solution up to the tip. In this case,the diameter of the air vent hole is preferably 1 to 50 μm. When thediameter is less than 1 μm, the air vent hole fails to sufficientlyfulfill the functions as an air vent. When the diameter exceeds 50 μm,the sharpness of the molded needle-like protruding portions is degraded.

Thus, in an aspect of the present invention, preferably, the transdermalabsorption material is a water-soluble polymer substance.

Preferably, the water-soluble polymer substance is any one ofhydroxyethyl starch, dextran, chondroitin sulfate, hyaluronic acid, andcarboxymethyl cellulose.

Furthermore, preferably, the drug is peptide, protein, nucleic acid,polysaccharide, a vaccine, a medical compound belonging to awater-soluble low-molecular-weight compound, or a cosmetic component.

As the water-soluble polymer substance used for the layer containing thedrug, one that does not interact with the contained drug is preferablyused. For example, if protein is used as the drug, when a chargeablepolymer substance is mixed with the protein, the protein and the polymersubstance electrostatically interact with each other to form anaggregate, which is cohered and precipitated. Therefore, when achargeable substance is used as the drug, a water-soluble polymersubstance with no charge such as hydroxyethyl starch or dextran ispreferably used.

To accomplish the object, another aspect of the present inventionprovides a transdermal absorption sheet in which a plurality of fineneedle-like protruding portions are arranged in a two-dimensional arrayon a surface of a sheet portion supported by a support, wherein a tip ofeach of the needle-like protruding portions contains a drug andhydroxyethyl starch, and a base of each of the needle-like protrudingportions contains hydroxyethyl starch and hyaluronic acid.

To accomplish the object, yet another aspect of the present inventionprovides a transdermal absorption sheet in which a plurality of fineneedle-like protruding portions are arranged in a two-dimensional arrayon a surface of a sheet portion supported by a support, in which a tipof each of the needle-like protruding portions contains a drug andchondroitin sulfate, and a base of each of the needle-like protrudingportions contains hydroxyethyl starch.

The transdermal absorption sheet according to the yet another aspect ofthe present invention allows construction of a transdermal absorptionsheet with microneedles which can be easily stuck into the skin andwhich are hard to break.

The transdermal absorption sheet and the manufacturing method thereforaccording to the present invention can provide a manufacturing methodfor a transdermal absorption sheet which enables the drug to concentrateat the needle-like protruding portions, while improving productionefficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a structure of a transdermal absorptionsheet according to an embodiment of the present invention.

FIG. 2A is a perspective view of a quadrangular pyramidal microneedlestructure in the transdermal absorption sheet.

FIG. 2B is a cross-sectional view of the quadrangular pyramidalmicroneedle structure in the transdermal absorption sheet.

FIG. 3A is a cross-sectional view of a conical microneedle structure inthe transdermal absorption sheet.

FIG. 3B is a cross-sectional view of the conical microneedle structurein the transdermal absorption sheet.

FIG. 4A is a diagram illustrating a production method for a mold.

FIG. 4B is a diagram illustrating the production method for the mold.

FIG. 4C is a diagram illustrating the production method for the mold.

FIG. 5 is a diagram illustrating a mold complex.

FIG. 6 is a diagram illustrating a mold in which microneedle structureswith tapered portions shaped like regular hexagons are arranged in ahoneycomb manner.

FIG. 7 is a diagram illustrating that enclosing members are formed onthe microneedle structures.

FIG. 8A is a diagram illustrating a manufacturing method for atransdermal absorption sheet according to the embodiment of the presentinvention.

FIG. 8B is a diagram illustrating the manufacturing method for thetransdermal absorption sheet according to the embodiment of the presentinvention.

FIG. 8C is a diagram illustrating the manufacturing method for thetransdermal absorption sheet according to the embodiment of the presentinvention.

FIG. 8D is a diagram illustrating the manufacturing method for thetransdermal absorption sheet according to the embodiment of the presentinvention.

FIG. 9A is a diagram illustrating motion of a transdermal absorptionmaterial in a filling step in the embodiment of the present invention.

FIG. 9B is a diagram illustrating the motion of the transdermalabsorption material in the filling step in the embodiment of the presentinvention.

FIG. 9C is a diagram illustrating the motion of the transdermalabsorption material in the filling step in the embodiment of the presentinvention.

FIG. 10A is a diagram illustrating the motion of the transdermalabsorption material observed when the viscosity of an upper layer is thesame as the viscosity of a lower layer.

FIG. 10B is a diagram illustrating the motion of the transdermalabsorption material observed when the viscosity of the upper layer isthe same as the viscosity of the lower layer.

FIG. 10C is a diagram illustrating the motion of the transdermalabsorption material observed when the viscosity of the upper layer isthe same as the viscosity of the lower layer.

FIG. 11A is a diagram illustrating a peeling-off step.

FIG. 11B is a diagram illustrating the peeling-off step.

FIG. 11C is a diagram illustrating the peeling-off step.

FIG. 12A is a side view of microneedles (projecting shapes) on atransdermal absorption sheet manufactured in an example.

FIG. 12B is a top view of the microneedles (projecting shapes) on thetransdermal absorption sheet manufactured in the example.

FIG. 13 is a diagram showing a filling rate in examples and comparativeexamples.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of a transdermal absorption sheet and amanufacturing method for the transdermal absorption sheet according tothe present invention is described below in detail using the drawings.

[Needle-Like Protruding Portions on the Transdermal Absorption Sheet]

FIG. 1 is a structure diagram of a transdermal absorption sheet 1 of anembodiment of the present invention.

The transdermal absorption sheet 1 of the embodiment of the presentinvention includes a support 2, a sheet portion 3, and a plurality ofmicroneedles 10 (needle-like protruding portions) arranged in atwo-dimensional array on a surface of the sheet portion 3.

The transdermal absorption sheet 1 is configured such that: a tip of themicroneedle 10 contains a drug and a transdermal absorption materialforming the microneedle 10; and a base of the microneedle 10 contains atransdermal absorption material forming the sheet portion 3.

That is, the transdermal absorption sheet preferably has a structure inwhich the transdermal absorption material forming the sheet portion 3enters into the base of the microneedle 10, instead of a structure inwhich the transdermal absorption material forming the microneedle 10 andthe transdermal absorption material forming the sheet portion 3 aredefinitely separated from each other as the portion of the microneedle10 and the portion of the sheet portion 3, respectively. This allowsformation of the transdermal absorption sheet 1 with the microneedles 10which can be easily stuck into the skin and which are hard to break.

FIG. 2A and FIG. 2B depict a preferred structure of the microneedle 10.

As depicted in a perspective view in FIG. 2A and a cross-sectional viewin FIG. 1B, the microneedle 10 formed on the transdermal absorptionsheet 1 needs to be shaped as follows so as to be stuck several hundredμm deep into the surface of the skin: (1) The tip is sufficientlypointed, and the diameter of the needle penetrating the skin issufficiently small (the aspect ratio of length/diameter is high), and(2) the microneedle has a sufficient strength (the microneedle does notbend).

Thus, to meet the requirement in (1), a thin and pointed shape isneeded. However, this is opposed to (2), and an excessively thin needleis bent at the tip or root thereof, whereas an excessively thick needlefails to be stuck into the skin. Thus, as depicted in FIG. 2A, a ridgeline 10A of the microneedle 10 is preferably shaped to be curved towardthe inside of the microneedle. The microneedle with such a shape can bemade difficult to bend by sufficiently sharpening the tip, whilewidening the root. Furthermore, the ridge lines 10A, 10A of aquadrangular pyramidal microneedle preferably extend from a quadrangularpyramidal surface 10C between the ridge lines 10A, 10A.

As for the shape of the microneedle 10, it is preferable that one side Xof a bottom surface is in a range of 0.1 μm or more and 1,000 μm or lesson, and a height Y is in a range of 0.3 μm or more and 3,000 μm or less.More preferably, one side X of the bottom surface is in a range of 10 μmor more and 400 μm or less, and the height is in a range of 30 μm ormore and 1,200 μm or less.

When the length of a segment connecting a start point and an end pointof the ridge line is represented as L, the maximum depth Z of curve ofthe ridge line 10A is preferably 0.04×L or more and 0.2×L or less.Furthermore, the radius of curvature R of a microneedle tip 10B, whichindicates sharpness of the microneedle 10, is preferably 20 μm or less,and more preferably 10 μm or less.

FIG. 2A and FIG. 2B depict the quadrangular pyramidal microneedle 10,but a microneedle shaped like a cone depicted in FIG. 3A and FIG. 3B andmicroneedles shaped like other pyramids such as a triangular pyramidpreferably have similar sizes. When the microneedle has a conical shape,the diameter X of the bottom surface is preferably within a range of 0.1μm or more and 1,000 μm or less, and more preferably 50 μm or more and500 μm or less. Furthermore, when the length of a segment connecting astart point and an end point of generatrix of the cone is represented asL, the maximum depth Z of curve of the cone is preferably 0.04×L or moreand 0.2×L or less.

As described above, the transdermal absorption sheet 1 is a protrudingportion array in which the microneedles 10 are arranged in atwo-dimensional array. To allow the microneedle 10 to be easily stuckinto the surface of the skin, it is important to sufficiently sharpenthe microneedle tip 10B. The radius of curvature R of the microneedletip 10B is preferably 10 μm or less. In order to form a microneedle 10having a tip with a radius of curvature R of 10 μm or less, an importantpoint is whether a solution of a transdermal absorption material can beinjected down to the tip (bottom) of needle-like recessed portionscorresponding to an inverted shape of the protrusion array formed in themold so as to allow accurate transfer.

Furthermore, the transdermal absorption sheet needs to contain a drug,but the drug is expensive in many cases. Thus, it is economicallyimportant to contain the drug in the transdermal absorption sheet sothat the drug concentrates at the portion of each microneedle.

[Manufacturing Method for the Transdermal Absorption Sheet]

A manufacturing method for the transdermal absorption sheet 1 accordingto the embodiment of the present invention is described.

<Production of the Mold>

FIGS. 4A to 4C are process diagrams illustrating production of a mold.

As depicted in FIG. 4A, an original plate 11 is first produced which isused to produce a mold 13 that allows the transdermal absorption sheet 1to be manufactured.

Two types of methods for producing the original plate 11 are available.A first method is to apply photo resist onto a Si substrate and then toexpose and develop the photo resist. Then, etching such as RIE (ReactiveIon Etching) is performed on the photo resist to form an array ofconical shape portions 12 (corresponding to the microneedles 10) on asurface of the original plate 11. When etching such as RIE is performedso as to form the conical shape portions 12 on the surface of theoriginal plate 11, the conical shape portions 12 can be formed bycarrying out the etching in an oblique direction while the Si substrateis being rotated.

A second method is a method of machining a metal substrate such as Niusing a cutting tool such as a diamond byte to form an array of theshape portions 12 (corresponding to the microneedles 10) shaped likequadrangular pyramids or the like on the surface of the original plate11.

Then, the mold 13 is produced. Specifically, as depicted in FIG. 4B, themold 13 is produced from the original plate 11. A method based on Nielectrocasting is used for normal production of the mold 13. Since theoriginal plate 11 has the shape portions of cones or pyramids(quadrangular pyramids, for example) with pointed tips, four methods arepossible which allow the original plate 11 to be peeled off from themold 13 after shape of the original plate 11 is precisely transferred tothe mold 13 and which enable the mold 13 to be inexpensivelymanufactured.

A first method is a method of pouring, into the original plate 11, asilicone resin containing PDMS (polydimethylsiloxane, for example,Sylgard™ 184 manufactured by Dow Corning Toray Co., Ltd.) with a curingagent added thereto, heating and curing the silicone resin at 100° C.,and then peeling the silicon resin off from the original plate 11. Asecond method is a method of pouring, into the original plate 11, a UVcuring resin that is cured when irradiated with ultraviolet light in anitrogen environment, and then peeling the UV curing resin off from theoriginal plate 11. A third method is a method of pouring a solution of aplastic resin such as polystyrene and PMMA (polymethylmethacrylate)dissolved into an organic solvent, into the original plate 11 coatedwith a release agent, volatilizing the organic solvent by means ofdrying to cure the plastic resin, and then peeling the plastic resin offfrom the original plate 11. A fourth method is a method of producing aninverted article by means of Ni electrocasting.

Thus, the mold 13 is produced in which needle-like recessed portions 15that are inverted shapes of cones or pyramids on the original plate 11are arranged in a two-dimensional array. The mold 13 produced asdescribed above is depicted in FIG. 4C. The mold 13 can be easilyproduced any number of times using any one of the above-described fourmethods.

FIG. 5 depicts an aspect of a mold complex 14 that is more preferable inexecuting the manufacturing method for the transdermal absorption sheet1 in the embodiment of the present invention. Portion (A) of FIG. 5depicts a cross-sectional view of the mold complex 14, portion (B) ofFIG. 5 depicts an enlarged view of the portion surrounded by the circlein portion (A). As shown in FIG. 5, the mold complex 14 includes themold 13 in which an air vent hole 15A is formed at the tip (bottom) ofeach needle-like recessed portion 15 and a gas permeable sheet 16laminated to a back surface of the mold 13 and formed of a material thatallows gas to pass though, while preventing liquid from passing through.The air vent hole 15A is formed as a through-hole that penetrates theback surface of the mold 13. In this regard, the back surface of themold 13 refers to a surface on the side of the tip of the needle-likerecessed portion 15. Thus, the tip of the needle-like recessed portion15 communicates with the atmosphere via the air vent hole 15A and thegas permeable sheet 16.

The use of the mold complex 14 as described above allows only the airpresent in the needle-like recessed portions 15 to be removed from theneedle-like recessed portions 15 while preventing permeation of thetransdermal absorption material solution contained in the needle-likerecessed portions 15. Thus, each needle-like recessed portion 15 can befilled with the solution of the transdermal absorption material down tothe tip (bottom) of the recessed portion. Consequently, the shape of theneedle-like recessed portion 15 can be precisely transferred to thetransdermal absorption material, allowing sharper microneedles 10(needle-like protruding portions) to be formed.

The diameter D of the air vent hole 15A is preferably within a range of1 to 50 μm. When the diameter D is less than 1 μm, the air vent holes15A cannot sufficiently accomplish the functions thereof. When thediameter D is more than 50 μm, it is likely that the sharpness of thetip of the molded microneedle 10 is degraded.

A gas permeable sheet 16 formed of a material that allows gas topermeate while preventing liquid from permeating, for example, latex(Asahi Kasei Chemicals Corporation) may be suitably used.

Furthermore, the needle-like recessed portion 15 preferably has atapered portion 15B with a tapered shape at an inlet portion of theneedle-like recessed portion 15. The angle θ of the tapered portion 15Bis preferably within a range of 10° to 20°. This taper angle rangeallows a pressing force to be exerted when the mold 13 is pressedagainst a surface of a two-layer film during a filling step describedbelow, and also allows the transdermal absorption material solution tobe well guided so as to collect in the needle-like recessed portions 15.

In this case, preferably, the bottom surface shape of the taperedportion 15B is formed like a hexagon, and the needle-like recessedportions 15 with the tapered portions 15B are arranged so as to form ahoneycomb structure, as depicted in FIG. 6. Thus, a pressing force isexerted when the mold 13 or the mold complex 14 is pressed against asurface of a two-layer film 20, facilitating even (uniform) filling ofthe adjacent needle-like recessed portions 15 with the transdermalabsorption material.

FIG. 7 is a diagram illustrating that enclosing members are formed onthe microneedle structures. Portion (B) of FIG. 7 is an enlarged view ofa portion enclosed by a circle in portion (A) of FIG. 7. As depicted inFIG. 7, the pressing surface of the mold 13 is preferably provided withenclosing members 15C that evenly partition the area of the transdermalabsorption material to be fed into the adjacent needle-like recessedportions 15 into areas so that the enclosing members 15C project fromthe pressing surface. As depicted in FIG. 7, the enclosing members 15Care provided at the ends of the tapered portions 15B of the adjacentneedle-like recessed portions 15, so as to project from the pressingsurface. The amount by which the enclosing member 15C projects from thepressing surface needs to be smaller than the thickness of the two-layerfilm, and is preferably comparable to the thickness of an upper layer.

FIG. 7 depicts an example in which the enclosing members 15C are formedon the mold complex 14. However, this configuration is applicable to thenormal mold 13 without the air vent hole 15A and the gas permeable sheet16.

Additionally, more preferably, the mold 13 itself is formed of a rawmaterial with high gas permeability. The oxygen permeability, which isrepresentative of the gas permeability, of the mold 13 is preferablymore than 1×10⁻¹² (mL/s·m²·Pa) and more preferably more than 1×10⁻¹⁰(mL/s·m²·Pa). Setting the gas permeability to within the above-describedrange allows the air present in the needle-like recessed portions 15 inthe mold 13 to be removed from the needle-like recessed portions 15.This improves transferability to allow sharper microneedles 10 to beformed.

Examples of materials with the above-described gas permeability includea silicone resin (for example, Sylgard 184® manufactured by Dow CorningToray Co., Ltd. or KE-131OST (product number) manufactured by Shin-EtsuChemical Co., Ltd.) a UV (ultraviolet) curing resin, and a plastic resin(for example, polystyrene or PMMA (polymethylmethacrylate) that ismelted or dissolved into a solvent. Among these materials, siliconerubber containing raw materials can be suitably used because of thedurability thereof against transfers based on repeated pressurizationand the easiness of the peel-off thereof from the raw material.Furthermore, metallic raw materials include Ni, Cu, Cr, Mo, W, Ir, Tr,Fe, CO, MgO, Ti, Zr, Hf, V, Nb, Ta, α-aluminum oxide, zirconium oxide,stainless steel (for example, a STAVAX™ material manufactured byBohler-Uddeholm KK), and alloys thereof.

<Manufacture of the Transdermal Absorption Sheet>

Now, the manufacturing method for the transdermal absorption sheet 1 ofthe embodiment of the present invention is described with reference toFIGS. 8A to 8D.

FIGS. 8A to 8D depict a normal type of the mold 13. However, theabove-described mold complex 14 is more preferably used.

(Preparation Steps for the Transdermal Absorption Material Solution)

A first transdermal absorption material solution 20A and a secondtransdermal absorption material solution 20B are prepared which areapplication solution to be applied onto a support 2 (hereinafter alsoreferred to as a substrate) to form a two-layer film 20.

In the present embodiment, a multilayer film formed on the support 2 isdescribed taking, as an example, the two-layer film 20 with an upperlayer and a lower layer. However, the present invention is not limitedto this number of layers. That is, on the support 2, the multilayer filmmay be formed which has a plurality of layers containing the transdermalabsorption material and for which, when the lowermost layer isrepresented as a first layer, the uppermost layer is represented as at-th layer (t≧2), and the viscosity of an n-th layer is represented asVn, then V1>V2≧ . . . ≧Vn≧ . . . ≧Vt, at least one layer other than thelowermost layer containing a drug.

The first transdermal absorption material solution 20A is to be thelower layer in the two-layer film 20. The first transdermal absorptionmaterial solution 20A contains no drug and is adjusted to have aflowable viscosity. Furthermore, the second transdermal absorptionmaterial solution 20B is to be the upper layer in the two-layer film 20.The second transdermal absorption material solution 20B contains a drugand is adjusted to have a viscosity at which higher flowability can beachieved than in the first transdermal absorption material solution 20Ain the lower layer.

In this regard, the flowable viscosity refers to a viscosity at whichthe layers flow when, during the filling step described below, the mold13 is pressed against the surface of the two-layer film 20 to apply apressure to the surface.

The viscosity of the first transdermal absorption material solution 20Ais preferably 200 Pa·s or more. Although the upper limit of theviscosity is not specified, because the first transdermal absorptionmaterial solution 20A needs to flow when pressed by the mold 13, theupper limit viscosity refers to the limit at which flowability can beachieved.

The viscosity of the second transdermal absorption material solution 20Bis preferably 2 to 30 Pa·s. If the viscosity is 2 Pa·s, whichcorresponds to the lower limit viscosity, the second transdermalabsorption material solution 20B flows when pressed by the mold 13, butdoes not flow and spread in the normal state.

The viscosity of the first transdermal absorption material solution 20A,which forms the lower layer, is preferably at least twice, morepreferably at least five times, particularly preferably at least 10times, and most preferably at least 20 times as high as the viscosity ofthe second transdermal absorption material solution 20B, which forms theupper layer. To achieve both coatability and flowability of theuppermost layer and the lowermost layer, the viscosity of the lowermostlayer is preferably at most 1,000 times as high as the viscosity of theuppermost layer.

The support 2 is not limited as long as the support 2 is shaped like athin film that can support the two-layer film 20. In particular, arelatively rigid plastic film such as PET (polyethylene terephthalate)or PEN (polyethylene naphthalate), a glass plate, paper, or the like maybe used.

The first and second transdermal absorption materials are not limited topolymer materials, natural materials, or the like as long as thematerials are polymer substances. However, the microneedles 10 of thetransdermal absorption material enters the skin, and thus, inparticular, water-soluble polymer substances are preferably used.

Preferably, the water-soluble polymer substance is any one ofhydroxyethyl starch, dextran, chondroitin sulfate, hyaluronic acid, andcarboxymethyl cellulose.

Furthermore, preferably, a biocompatible resin is used as a polymermaterial. It is preferable to use, as such a resin, sugar such asglucose, maltose, or pullulan, protein such as gelatin, polylactate, ora biodegradable polymer such as a lactic acid-glycollic acid copolymer.Among these resins, a gelatin containing raw material can tightlycontact many supports 2 and has a high gel strength enough to allow thegelatin containing raw material to be used as a material that is gelled.Thus, the gelatin containing raw material can be suitably used during apeeling-off step described below because the raw material can be broughtinto tight contact with the support 2. The density of the resin ispreferably such that 10 to 40% resin polymer is contained in thesolution, though the density depends on the type of the material.Additionally, a solvent used for dissolution may be other than hot wateras long as the solvent has volatility, and alcohol may be used. A drugto be supplied to the inside of the human body may be dissolved into asolution of the polymer resin in accordance with an intended use.

Examples of a method for adjusting the viscosity of each layer include amethod of selecting an appropriate polymer substance, a method ofadjusting the content of a solvent in the polymer substance, and amethod of mixing different polymer substances in an appropriate ratio.

Preferably, for a relatively low viscosity, hydroxyethyl starch,dextran, chondroitin sulfate, glucose, maltose, pullulan, gelatin,polylactate, lactic acid-glycollic acid copolymer, or the like is usedas a transdermal absorption material contained in a low-viscosity layer,and a material obtained by adding a suitable amount of a high-viscositypolymer substance such as hyaluronic acid or carboxymethyl cellulose tothe transdermal absorption material contained in the low-density layeris used as a transdermal absorption material contained in ahigh-viscosity layer.

The use of a transdermal absorption material with the above-describedcombination allows a transdermal absorption sheet with a drugconcentrating at microneedles to be manufactured with high productionefficiency.

More preferably, the transdermal absorption material forming thelow-viscosity layer contains at least one selected from the groupconsisting of hydroxyethyl starch, dextran, and chondroitin sulfate, andthe transdermal absorption material forming the high-viscosity layercontains at least one selected from the group consisting of hydroxyethylstarch, dextran, and chondroitin sulfate and at least one selected fromthe group consisting of hyaluronic acid and carboxymethyl cellulose.

Preferably 50 wt % or more, more preferably 0 wt % or more, and muchmore preferably 90 wt % or more of the transdermal absorption materialforming the low-viscosity layer is a polymer substance selected from thegroup consisting of hydroxyethyl starch, dextran, and chondroitinsulfate. Preferably 50 wt % or more, more preferably 80 wt % or more,and much more preferably 90 wt % or more of the transdermal absorptionmaterial forming the high-viscosity layer is a polymer substanceselected from the group consisting of hydroxyethyl starch, dextran,chondroitin sulfate, hyaluronic acid, and carboxymethyl cellulose.

Furthermore, when the tip of each needle-like protruding portion in thetransdermal absorption sheet contains: drug; and at least one selectedfrom the group consisting of hydroxyethyl starch, dextran andchondroitin sulfate, and the base of the needle-like protruding portionin the transdermal absorption sheet contains: at least one selected fromthe group consisting of hydroxyethyl starch, dextran and chondroitinsulfate; and at least one selected from the group consisting ofhyaluronic acid and carboxymethyl cellulose, the transdermal absorptionsheet has high drug utilization efficiency and is hard to break.Preferably, the tip of the needle-like protruding portion containshydroxyethyl starch, and the base of the needle-like protruding portioncontains hydroxyethyl starch and hyaluronic acid.

In the transdermal absorption sheet, preferably 50 wt % or more, morepreferably 80 wt % or more, and much more preferably 90 wt % or more ofthe transdermal absorption material forming the tip of the needle-likeprotruding portion is a polymer substance selected from the groupconsisting of hydroxyethyl starch, dextran, and chondroitin sulfate. Inthe transdermal absorption sheet, preferably 50 wt % or more, morepreferably 80 wt % or more, and much more preferably 90 wt % or more ofthe transdermal absorption material forming the base of the needle-likeprotruding portion is a polymer substance selected from the groupconsisting of hydroxyethyl starch, dextran, chondroitin sulfate,hyaluronic acid, and carboxymethyl cellulose.

Furthermore, the drug contained in the second transdermal absorptionmaterial solution 20B is not limited as long as the drug accomplishesthe functions of the drug, but is particularly preferably selected fromthe group consisting of peptide, protein, nucleic acid, polysaccharide,a vaccine, a medical compound belonging to a water-solublelow-molecular-weight compound, or a cosmetic component.

Additionally, as the water-soluble polymer substance contained in thesecond transdermal absorption material solution 20B, one that does notinteract with the drug contained is preferably used. For example, ifprotein is used as the drug, when a chargeable polymer substance ismixed with the protein, the protein and the polymer substanceelectrostatically interact with each other to form an aggregate, whichis cohered and precipitated. Therefore, when a chargeable substance isused in the drug, a water-soluble polymer substance with no charge suchas hydroxyethyl starch or dextran is preferably used.

For a method for preparing the second transdermal absorption materialsolution 20B, when a water-soluble polymer (gelatin or the like) is usedfor example, the second transdermal absorption material solution 20B canbe manufactured by dissolving water-soluble powder into water, and afterthe dissolution, adding a medicine to the solution. If the material isdifficult to dissolve into water, the material may be dissolved onheating. The temperature may be selected as needed depending on the typeof the polymer material, but the material is preferably heated atapproximately 60° C. (laminating step).

As depicted in FIG. 8A, the first transdermal absorption materialsolution 20A with a high viscosity is applied onto the support 2 to forma lower layer, and the second transdermal absorption material solution20B with a low viscosity is applied onto the lower layer to form anupper layer. Thus, the two-layer film 20 consisting of the lower layerwith the high viscosity and the upper layer with the low viscosity andhaving a viscosity difference is laminated on the support 2. In thiscase, for the upper layer formed of the second transdermal absorptionmaterial solution 20B, the needed coating amount, that is, the neededcoating thickness, of the second transdermal absorption materialsolution 20B is set based on the post-molding set solids amount of themicroneedles 10 to be molded and the solids concentration of the secondtransdermal absorption material solution 20B.

That is, for one unit of the needle-like recessed portion 15, the neededcoating amount per needle-like recessed portion is calculated from a setvalue for the solids amount (for example, the material is solidified bymeans of drying or the like up to a moisture amount at which themicroneedles 10 have elasticity) of the second transdermal absorptionmaterial 20B to be fed into the needle-like recessed portion 15 and thesolids concentration of the second transdermal absorption materialsolution 20B prepared in the preparing step for the transdermalabsorption material. Then, the layer thickness of the upper layer iscalculated by dividing a total coating amount resulting frommultiplication of the coating amount per needle-like recessed portion bythe number of needle-like recessed portions 15 formed in the mold 13, bythe size of the area of the two-layer film 20 which is pressed againstthe mold 13. In this regard, the calculation for the size of the areapressed may be executed on the assumption that the mold 13 has noneedle-like recessed portion and is flat.

The applied film thickness of the first transdermal absorption materialsolution 20A forming the lower layer is not particularly limited but ispreferably approximately 300 to 500 μm because an excessively largethickness makes the transdermal absorption material useless.

A coater that applies the first and second transdermal absorptionmaterial solutions 20A and 20B is not particularly limited, but meteringcoaters such as a slot coater, a rod coater, a knife coater, and agravure coater which facilitate application of a given amount arepreferred because the second transdermal absorption material solution20B needs to be applied so as to achieve an accurate coating thickness.

For the above-described laminating step, besides the basic aspect inwhich the two-layer film 20 is formed by applying the lower layer ontothe support 2 and applying the upper layer onto the lower layer, thefollowing aspects may be carried out.

<Aspect 1> A method of applying the first transdermal absorptionmaterial solution 20A onto the support 2 to form the lower layer, thentemporarily drying the lower layer, and applying the second transdermalabsorption material solution 20B to the dried lower layer to form theupper layer.

<Aspect 2> A method of applying the first transdermal absorptionmaterial solution 20A onto the support 2 to form the lower layer, thentemporarily drying the lower layer, applying the second transdermalabsorption material solution 20B to the dried lower layer to form theupper layer, then temporarily drying the upper layer, and then allowingthe resultant structure to absorb water to form the two-layer film 20.

<Aspect 3> A method of applying the first transdermal absorptionmaterial solution 20A onto the support 2 and drying the firsttransdermal absorption material solution 20A to form the lower layer,while applying the second transdermal absorption material solution 20Bonto the support 2 and drying the second transdermal absorption materialsolution 20B to form the lower layer, peeling the upper layer off fromthe support 2 and laminating the upper layer to the lower layer, andthen allowing the resultant structure to absorb water to form thetwo-layer film 20.

In Aspects 1 to 3, the drying of the upper layer and the lower layer ispreferably preformed such that the water content of the layers is 20 wt% or less.

(Filling Step)

As depicted in FIGS. 8B and 8C, the needle-like recessed portions 15 arefilled with the transdermal absorption material by pressing the mold 13produced as described above against the surface of the two-layer film 20supported by the support 2 to allow the two-layer film 20 to flow.

In such a filling step, the first transdermal absorption materialsolution 20A forming the lower layer and the second transdermalabsorption material solution 20B forming the upper layer have aviscosity difference and thus flows in a manner described below.

As depicted in FIG. 9A, the mold 13 is positioned above the two-layerfilm 20 formed on the support 2. Then, as depicted in FIG. 9B, the mold13 is pressed against the surface of the two-layer film 20. Thus, sincethe upper layer in the two-layer film 20 has a lower viscosity than thelower layer in the two-layer film 20, first, the second transdermalabsorption material solution 20B with the lower viscosity in the upperlayer flows into the needle-like recessed portions 15. Thus, theneedle-like recessed portions 15 in the mold 13 are each filled onlywith the second transdermal absorption material solution 20B with thelower viscosity, but not filled up to the tip of the needle-likerecessed portions 15.

As depicted in FIG. 9C, the mold 13 is further continuously pressedagainst the surface of the two-layer film 20, the first transdermalabsorption material solution 20A in the lower layer, having a nexthigher viscosity than in the upper layer, acts to flow into theneedle-like recessed portions 15. Thus, the second transdermalabsorption material solution 20B already contained in the needle-likerecessed portions 15 is pushed toward the tip side of each needle-likerecessed portion 15.

Therefore, in the laminating step, when the layer thickness of the upperlayer is set based on the solids amount of the microneedles 10 and thesolids concentration of the second transdermal absorption materialsolution 20B, an approximately total amount of second transdermalabsorption material solution 20B containing the drug is filled into theneedle-like recessed portions 15. As a result, the drug can beconcentrated at the microneedles 10 on the molded transdermal absorptionsheet 1.

The pressure at which the mold 13 is pressed against the surface of thetwo-layer film 20 is preferably the pressure at which mold 13 can bedisplaced at a constant speed of 10 to 2,000 μm/min toward the support2.

When the speed of the displacement exceeds 2,000 μm/min, the secondtransdermal absorption material solution 20B in the upper layer flowsand escapes out of the needle-like recessed portions 15 before thesecond transdermal absorption material solution 20B in the upper layeris completely filled into the needle-like recessed portions 15.Furthermore, when the speed of the displacement is less than 10 μm/min,the filling step has a prolonged duration, reducing productionefficiency.

Additionally, when the duration of the filling step is to be shortened,the mold 13 can be pressed against the two-layer film 20 so as to bedisplaced toward the support 2 while being gradually accelerated withina speed range of 10 to 2,000 μm/min.

Many of the drugs used have the risk of being thermally decomposed, andthus, the laminating step, the filling step, and the peeling-off step inthe present embodiment are preferably executed at normal temperature.Furthermore, also when the solidifying step is executed by means ofdrying, drying temperature is preferably low enough to prevent the drugfrom being decomposed.

FIGS. 10A to 10C are comparative diagrams illustrating the embodiment ofthe present invention and depicting motion of the transdermal absorptionmaterial observed when a lower layer 30A and an upper layer 30B forminga two-layer film 20 have the same viscosity.

As depicted in FIG. 10A, the mold 13 is positioned above the two-layerfilm 20, and as depicted in FIG. 10B, the mold 13 is pressed against thesurface of the two-layer film 30 supported by the support 2. Thepressure at which the mold 13 is pressed against the two-layer film 20is similar to the pressure in the embodiment of the present inventiondepicted in FIG. 9B.

However, as seen in FIG. 10B, when the lower layer 30A and the upperlayer 30B have the same viscosity, pressing the mold 13 causes the lowerlayer 30A and the upper layer 30B to start flowing at the same time.Thus, as depicted in FIG. 10C, the needle-like recessed portions 15 arefilled with the lower layer 30A and the upper layer 30B in a state wherethe two-layer film 30 is retained. That is, a portion of the upper layer30B is filled into a wall surface side of each needle-like recessedportion 15, and a portion of the lower layer 30A is filled into acentral portion side of the needle-like recessed portion 15 so as to beenveloped by a portion of the upper layer 30B.

Thus, when the lower layer 30A and the upper layer 30B has the sameviscosity, the drug cannot be concentrated at the microneedle 10 of themolded transdermal absorption sheet 1.

<Solidifying Step>

In the solidifying step, the two-layer film 20 is solidified with themold 13 kept pressed against the surface of the two-layer film 20, thatis, in a state depicted in FIG. 8C. Strictly speaking, the transdermalabsorption materials having formed the two-layer film 20 is solidifiedin the solidification step because the upper layer is filled into theneedle-like recessed portion 15 so that the inside of the needle-likerecessed portion 15 is not in the two-layer film state. However, forsimplification, the solidification is referred to as a solidification ofthe two-layer film.

As a method for the solidification, drying solidification can besuitably performed.

In a method for drying solidification, warm air is blown against thetwo-layer film. The warm air is preferably dehumidified and has atemperature of 35° C. and a relative humidity of 50% or less, and morepreferably 10% or less, for example. When warm air at high temperatureis flown for drying, an excessively high temperature of the warm air maycause, depending on the type of a medicine used, for example,decomposition of the medicine on heating, leading to a change in theefficacy of the medicine. Thus, care needs to be taken for thetemperature of the blown warm air.

The solidified transdermal absorption material solution causes thetransdermal absorption material to be contracted more significantly thanin the case of filling the transdermal absorption material into theneedle-like recessed portions 15, facilitating peel-off of thetransdermal absorption material from the mold 13. Furthermore, in thedrying solidification, an excessively low moisture amount of thetransdermal absorption material makes peel-off difficult, and thus, themoisture amount at which elasticity is kept is preferably maintained.Specifically, drying is preferably stopped when the moisture amount is10 to 20%, though the moisture amount depends on the type of thetransdermal absorption material forming the microneedle 10.

(Peeling-Off Step)

As depicted in FIG. 8D, in the peeling-off step, the solidifiedtwo-layer film 20 supported by the support 2 is peeled off from the mold13. Specifically, as depicted in FIG. 11A, the mold 13 is poisoned onthe lower side, and the support 2 supporting the two-layer film 20 ispositioned on the upper side. Then, as depicted in FIG. 11B, a peel-offsheet 22 with an adhesive layer formed thereon is attached to thesupport 2. For example, a PET film may be adopted as the materialpeel-off sheet 22.

Then, the two-layer film 20 is peeled off from the mold 13 by flippingthe peel-off sheet 22 up at an end thereof. Thus, a transdermalabsorption sheet in a state where the peel-off sheet 22 is attachedthereon is manufactured as depicted in FIG. 11C, and subsequently, thepeel-off sheet 22 is peeled off from the support 2. As a result, thetransdermal absorption sheet 1 is manufactured.

Furthermore, as another aspect of the peeling-off method, a method,though not depicted in the drawings, is available which involves:attaching a plurality of suckers to the support 2, sucking an air sothat the suckers adsorb onto the support 2, and pulling the suckers topeel off the two-layer film 20.

The peeing-off step of peeling the solidified two-layer film 20 off fromthe mold 13 is an important step. Normally, as in the embodiment, when astructure with the microneedles 10 with a high aspect ratio is peeledoff from the mold 13, the large contact area of the microneedles 10causes high stress to be exerted on the microneedles 10, which are thusdestroyed. The microneedles 10 then remain in the needle-like recessedportions 15 of the mold 13 instead of being peeled off from the mold 13.Thus, the resultant transdermal absorption sheet 1 has fatal defects.

Based on this, in the present embodiment, the material constituting themold 13 is preferably composed of a material that significantlyfacilitates peel-off. Furthermore, when the material constituting themold 13 is a high-elastic soft material, the stress exerted on themicroneedles 10 can be relaxed at the time of peel-off.

Additionally, to allow evaporation of moisture remaining in themicroneedles 10 on the surface of the transdermal absorption sheet 1,dry air may be blown against the microneedles 10 or vacuum drying may beperformed on the microneedles 10, after peel-off. Specifically,immediately before packing, the moisture amount of the transdermalabsorption sheet 1 is set to 10% or less, and desirably 5% or less.Alternatively, the transdermal absorption sheet 1 may be packed togetherwith a drying material so as to set the moisture amount of thetransdermal absorption sheet 1 to 10% or less, and desirably 5% or less,after packing.

EXAMPLES

Specific examples of the manufacturing method for the transdermalabsorption sheet 1 in the present invention are described below.

[Test 1]

Test 1 involved determining how the rate of the drug concentrated at themicroneedles 10 (filling rate) varied between cases where the conditionsfor the manufacturing method for the transdermal absorption sheet 1according to the embodiment of the present invention were met and caseswhere the conditions were not met.

<Production of the Mold>

FIGS. 12A and 12B depict the projecting shape of the transdermalabsorption sheet 1 manufactured. FIG. 12A is a side view, and FIG. 12Bis a top view.

As depicted in FIGS. 12A and 12B, the projecting shape is such that aconical microneedle 10 (needle-like protruding portion) with a bottomsurface diameter X of 420 μm and a height Y of 700 μm is loaded on ahexagonal truncated pyramid 24. The hexagonal truncated pyramid 24 has:a hexagonal bottom surface with a length of 404 μm on one side S and adiameter W of 700 μm; a circular top surface with a diameter of 420 μm;and a height H of 420 μm.

The hexagonal pyramid 24 corresponds to the tapered portion 15B of themold 13.

The pitch P between the microneedle 10 and the microneedle 10 was set to700 μm, and the radius of curvature R of the microneedle tip 10B was setto at most 5 μm. Furthermore, the taper angle θ of the hexagonal pyramid24 was set to 16.7°.

The original plate 11 was produced by forming, by means of grinding, 37projecting shapes as described above in a honeycomb array depicted inFIG. 6 on a surface of a flat Ni plate of a length of 40 mm on one side.

Then, on the original plate 11, silicone rubber (SILASTIC™, MDX4-4210(product number) manufactured by Dow Corning Toray Co., Ltd.) was formedinto a film of thickness of 692 μm. The film was thermally cured withthe microneedle tips of the original plate 11 projecting from a filmsurface by 50 μm, and then peeled off. Thus, an inverted article ofsilicone rubber with air vent holes (through-holes) of diameter ofapproximately 30 μm was produced. The 37 needle-like recessed portions15, which are inverted shapes of the above-described projecting shapes,are arranged in a central area of the inverted article in a honeycombstructure. The central area corresponds to the pressing surface to bepressed against the two-layer film. Thus, the mold 13 with a diameter of5 mm was produced by cutting off the entire area of the inverted articleother than the central area. Then, the mold complex 14 was formed bylaminating the gas permeable sheet to the back surface of the mold 13.

Example 1 Preparation of the Transdermal Absorption Material Solution

The first transdermal absorption material solution 20A forming the lowerlayer was prepared as a mixed water solution resulting from mixture of awater solution with a hydroxyethyl starch (molecular weight of 70,000;manufactured by Fresenius Kabi) concentration of 39 wt % and a watersolution with a sodium hyaluronate (molecular weight of 900,000 to1,050,000; manufactured by Maruha Nichiro Corporation) concentration of1 wt %.

Furthermore, the second transdermal absorption material solution 20Bforming the upper layer was prepared as mixed solution which contained awater solution with a hydroxyethyl starch concentration of 14 wt % andin which 0.25 wt % human growth hormone (growth hormone, human,recombinant, for biochemistry; manufactured by Wako Pure ChemicalIndustries, Ltd.) was contained as a drug and FITC (fluorosceinisothiocyanate: manufactured by PD Research, FACS-D1 (product number)),which is a type of fluorescent dye, was also contained so as to have anFITC concentration of 0.001 wt %.

<Laminating Step>

The first transdermal absorption material solution 20A prepared asdescribed above was applied onto the support 2 to a thickness ofapproximately 300 μm and dried at 35° C. and at a relative humidity of40% to form a lower layer with a high viscosity. A glass plate was usedas the support 2, and this also applied to the other examples.Subsequently, the second transdermal absorption material solution 20Bprepared as described above was applied onto the lower layer to athickness of 110 μm form an upper layer of a low viscosity. Thus, thetwo-layer film 20 with a viscosity difference was formed on the support2.

The following method was used as an evaluation method for the viscosityin the layer state of the lower layer and the upper layer. First,immediately before the filling step, the lower layer and the upper layerare focused on by means of micro-Raman spectroscopy. The signal ratiobetween CH groups and OH groups in the corresponding site was measuredfor each of the lower and upper layers. The focus is determined bypredicting the positions of the upper layer and the lower layer based ondistances from the uppermost surface. Then, the water content of thelower layer is calculated by determining the water content at themeasured signal ratio based on a standard line indicative of therelation between the water content of the substance in the samecomposition as that of a pre-produced lower layer and the signal ratioof CH groups and OH groups. Then, the viscosity of the lower layer isobtained by measuring the viscosity, at the calculated water content, ofthe substance in the same composition as that of the lower layer (TheBohlin Gemini HR nano Reometer System manufactured by MalvernInstruments Ltd.). The viscosity value of the upper layer is calculatedin a manner similar to the manner for the lower layer.

The viscosity of the high-viscosity lower layer determined using theabove-described evaluation method was 1,000 Pa·s. The viscosity of thelow-viscosity upper layer determined using the above-describedevaluation method was 2 Pa·s. The lower layer had a viscosity 500 timeshigher than the viscosity of the upper layer.

<Filling Step>

Immediately after the formation of the two-layer film 20 on the support2 by means of coating, the mold 13 produced as described above wasbrought into tight contact with the surface of the two-layer film 20.The mold 13 was pressed toward the support 2 so as to be displaced at aconstant speed of 200 μm/min, thus filling the inside of eachneedle-like recessed portion 15 of the mold 13 with the transdermalabsorption material. Once the needle-like recessed portion 15 wascompletely filled with the transdermal absorption material, the pressingof the mold 13 was stopped.

<Solidifying Step and Peeling-Off Step for the Two-Layer Film>

While a pressure of 10 g/cm² was being applied to the two-layer film 20through the upper surface of the mold 13, the two-layer film 20 wassolidified by being dried at 35° C. and at a relative humidity of 40%.Subsequently, the transdermal absorption sheet 1 was produced by peelingthe mold 13 off from the two-layer film.

Example 2

In Example 2, the transdermal absorption sheet 1 was produced underconditions similar to the conditions for Example 1 except for thecomposition of the first transdermal absorption material solution 20Afor forming the lower layer.

That is, a mixed water solution with a hydroxyethyl starch concentrationof 39.5 wt % and a sodium hyaluronate concentration of 0.5 wt % wasapplied onto the support 2 to a thickness of approximately 300 μm anddried at 35° C. and at a relative humidity of 40% to form the lowerlayer. Subsequently, the second transdermal absorption material solution20B with the same composition as that in Example 1 was applied onto thelower layer to a thickness of 110 μm form the upper layer. Thus, thetwo-layer film 20 was formed. The viscosity of the lower layer producedas described above was 200 Pa·s. The viscosity of the upper layerproduced as described above was 2 Pa·s. The lower layer had a viscosity100 times higher than the viscosity of the upper layer.

Example 3

In Example 3, the transdermal absorption sheet 1 was produced underconditions similar to the conditions for Example 1 except for thecomposition of the first transdermal absorption material solution 20Afor forming the lower layer.

That is, a mixed water solution with a hydroxyethyl starch concentrationof 39.75 wt % and a sodium hyaluronate concentration of 0.25 wt % wasapplied onto the support 2 to a thickness of approximately 300 μm anddried at 35° C. and at a relative humidity of 40% to form the lowerlayer. Subsequently, the second transdermal absorption material solution20B with the same composition as that in Example 1 was applied onto thelower layer to a thickness of 110 μm form the upper layer. Thus, thetwo-layer film 20 was formed. The viscosity of the lower layer producedas described above was 10 Pa·s. The viscosity of the upper layerproduced as described above was 2 Pa·s. The lower layer had a viscosityfive times higher than the viscosity of the upper layer.

Example 4

In Example 4, the transdermal absorption sheet 1 was produced underconditions similar to the conditions for Example 1 except that thecomposition of the second transdermal absorption material solution 20Bfor forming the upper layer was changed from the composition in Example1.

That is, the same first transdermal absorption material solution 20A asthat in Example 1 was applied onto the support 2 to a thickness ofapproximately 300 μm and dried at 35° C. and at a relative humidity of40% to form the lower layer. A mixed solution was prepared by addinghuman growth hormone as a drug and FITC, to a mixed water solution witha hydroxyethyl starch concentration of 13.9 wt % and a sodiumhyaluronate concentration of 0.1 wt %, so as to have a human growthhormone concentration of 0.25 wt % and an FITC concentration of 0.001 wt%. Subsequently, the surface of the lower layer was coated with theprepared mixed solution to a thickness of 110 μm. Thus, the two-layerfilm 20 was formed on the support 2. The viscosity of the lower layerproduced as described above was 1,000 Pa·s. The viscosity of the upperlayer produced as described above was 30 Pa·s. The lower layer had aviscosity 33 times higher than the viscosity of the upper layer.

Example 5

In Example 5, the transdermal absorption sheet 1 was produced underconditions similar to the conditions for Example 1 except that thecomposition of the first transdermal absorption material solution 20Afor forming the lower layer and the composition of the secondtransdermal absorption material solution 20B for forming the upper layerwere changed from the compositions in Example 1.

That is, a water solution with a hydroxyethyl starch concentration of 40wt % was applied onto the support 2 to a thickness of approximately 300μm and dried at 35° C. and at a relative humidity of 40% to form thelower layer. A mixed solution was prepared by adding BSA (Albumin, frombovine serum manufactured by SIGMA Corporation) as a drug and FITC, to awater solution with a sodium chondroitin sulfate (sodium chondroitinsulfate specified in Japanese Pharmaceutical Codex; manufactured byMaruha Nichiro Corporation) concentration of 14 wt %, so as to have aBSA concentration of 0.25 wt % and an FITC concentration of 0.001 wt %.Subsequently, the surface of the lower layer was coated with theprepared mixed solution to a thickness of 110 μm. Thus, the two-layerfilm 20 was formed on the support 2. The viscosity of the lower layerproduced as described above was 200 Pa·s. The viscosity of the upperlayer produced as described above was 10 Pa·s. The lower layer had aviscosity 20 times higher than the viscosity of the upper layer.

Example 6

In Example 6, the composition of the first transdermal absorptionmaterial solution 20A for forming the lower layer and the composition ofthe second transdermal absorption material solution 20B for forming theupper layer were changed from the compositions in Example 1, and thelower layer that had not been dried was coated with the upper layer.Furthermore, the layer thicknesses of the lower layer and the upperlayer were changed. As to the other conditions, the transdermalabsorption sheet 1 was produced under conditions similar to Example 1.

That is, a mixed water solution with a hydroxyethyl starch concentrationof 48.8 wt % and a sodium hyaluronate concentration of 1.2 wt % wasapplied onto the support 2 to a thickness of approximately 240 μm toform the lower layer. A mixed solution was prepared by adding humangrowth hormone as a drug and FITC, to a water solution with ahydroxyethyl starch concentration of 50 wt % so as to have a humangrowth hormone concentration of 0.25 wt % and an FITC concentration of0.001 wt %. Subsequently, the upper layer was formed by coating thesurface of the lower layer that had not been dried with the preparedmixed solution to a thickness of 15 μm. Thus, the two-layer film 20 wasformed on the support 2. The viscosity of the lower layer produced asdescribed above was 1,000 Pa·s. The viscosity of the upper layerproduced as described above was 2 Pa·s. The lower layer had a viscosity500 times higher than the viscosity of the upper layer.

Example 7

In Example 7, the compositions of the lower layer and the upper layerwere similar to the compositions in Example 1, but the two-layer filmwas formed by applying the upper layer, then drying the upper layer andfurther applying water to the upper layer for humidification. As to theother conditions, the transdermal absorption sheet 1 was produced underconditions similar to Example 1.

That is, the same first transdermal absorption material solution 20A asthat in Example 1 was applied onto the support 2 to a thickness ofapproximately 300 μm and dried at 35° C. and at a relative humidity of40% to form the lower layer. Subsequently, the same second transdermalabsorption material solution 20B as that in Example 1 was applied ontothe lower layer to a thickness of 110 μm and dried at 35° C. and at arelative humidity of 40% to form the upper layer. Then, water wasapplied onto the upper layer to a thickness of 100 μm forhumidification. Thus, the two-layer film 20 was formed on the support 2.The viscosity of the lower layer produced as described above was 1,000Pa·s. The viscosity of the upper layer produced as described above was 2Pa·s. The lower layer had a viscosity 500 times higher than theviscosity of the upper layer.

Example 8

In Example 8, the compositions of the lower layer and the upper layerwere similar to the compositions in Example 1. However, the lower layerand the upper layer were separately applied onto the support 2 anddried, and then, the upper layer was peeled off from the support 2 andlaminated to the lower layer, and water was applied for humidification.The two-layer film 20 was thus formed. As to the other conditions, thetransdermal absorption sheet 1 was produced under conditions similar toExample 1.

That is, the same first transdermal absorption material solution 20A asthat in Example 1 was applied onto the support 2 to a thickness ofapproximately 300 μm and dried at 35° C. and at a relative humidity of40% to form the lower layer. Furthermore, the same second transdermalabsorption material solution 20B as that in Example 1 was applied ontothe support 2 to a thickness of 110 μm and dried at 35° C. and at arelative humidity of 40% to form the upper layer.

The upper layer was peeled off from the support 2 and laminated to thelower layer so as to tightly contact with the lower layer, and then,water was applied onto the upper layer to a thickness of 100 μm to formthe two-layer film 20. The viscosity of the lower layer produced asdescribed above was 1,000 Pa·s. The viscosity of the upper layerproduced as described above was 2 Pa·s. The lower layer had a viscosity500 times higher than the viscosity of the upper layer.

Example 9

In Example 9, the compositions of the lower layer and the upper layerwere similar to the compositions in Example 1. However, the two-layerfilm was formed by applying the upper layer onto the lower layer appliedonto the support 2 without drying the lower layer. Furthermore, adisplacement speed at which the mold 13 was pressed against thetwo-layer film 20 was changed from the displacement speed in Examples 1to 8. As to the other conditions, the transdermal absorption sheet 1 wasproduced under conditions similar to Example 1.

That is, the same first transdermal absorption material solution 20A asthat in Example 1 was applied onto the support 2 to a thickness ofapproximately 300 μm to form the lower layer. Subsequently, the samesecond transdermal absorption material solution 20B as that in Example 1was applied onto the lower layer to a thickness of 110 μm to form theupper layer. Thus, the two-layer film 20 was formed on the support 2.The viscosity of the lower layer produced as described above was 1,000Pa·s. The viscosity of the upper layer produced as described above was 2Pa·s. The lower layer had a viscosity 500 times higher than theviscosity of the upper layer.

The mold 13 was brought into tight contact with the surface of thetwo-layer film 20 formed as described above. The mold 13 was pressedtoward the support 2 while being accelerated over 30 seconds at adisplacement speed from 10 μm/min to 200 μm/min, to fill the needle-likerecessed portions 15 in the mold 13 with the transdermal absorptionmaterial. The displacement of the mold 13 was stopped when theneedle-like recessed portions 15 were completely filled with thetransdermal absorption material.

Comparative Example 1

Comparative Example 1 is a case where the transdermal absorption sheet 1was produced with the same viscosity set for the lower layer and theupper layer.

That is, a water solution with a hydroxyethyl starch concentration of 40wt % was applied onto the support 2 to a thickness of approximately 300μm and dried at 35° C. and at a relative humidity of 40% to form thelower layer. Subsequently, the upper layer was formed by coating thesurface of the lower layer with a mixed solution to a thickness of 110μm, the mixed solution containing a water solution with a hydroxyethylstarch concentration of 14 wt %, with 0.25 wt % human growth hormonecontained therein as a drug and FITC also contained therein so as tohave an FITC concentration of 0.001 wt %. The viscosity of the lowerlayer produced as described above was 2 Pa·s. The viscosity of the upperlayer produced as described above was 2 Pa·s. The lower layer and theupper layer had the same viscosity.

Comparative Example 2

Comparative Example 2 is a case where the transdermal absorption sheet 1was produced with the viscosity of the lower layer set higher than theviscosity of the upper layer.

That is, a water solution with a sodium chondroitin sulfateconcentration of 40 wt % was applied onto the support 2 to a thicknessof approximately 300 μm and dried at 35° C. and at a relative humidityof 40% to form the lower layer. A mixed solution was prepared by addinghuman growth hormone as a drug and FITC, to a water solution with ahydroxyethyl starch concentration of 14 wt % so as to have a humangrowth hormone concentration of 0.25 wt % and an FITC concentration of0.001 wt %. Subsequently, the upper layer was formed by coating thesurface of the lower layer with the prepared mixed solution to athickness of 110 μm. The viscosity of the upper layer produced asdescribed above was 200 Pa·s. The viscosity of the lower layer producedas described above was 10 Pa·s. The upper layer had a higher viscositythan the lower layer.

(Evaluation Method for Test Results)

For the transdermal absorption sheets in Examples 1 to 9 and ComparativeExamples 1 and 2 produced as described above, the following wasexamined: the filling rate at which the microneedles 10 (needle-likeprotruding portions) were filled with the second transdermal absorptionmaterial solution 20B containing the drug, with respect to the totalamount of the second transdermal absorption material solution 20B. Thisenabled evaluation of how the drug was successfully concentrated at theportion of the microneedles 10. As a measuring method for the fillingrate, the following two methods were adopted.

<Measuring Method for the Filing Rate 1>

In a measuring method for the filling rate 1, a confocal florescencemicroscope (manufactured by NIKON CORPORATION; C1plus+TE2000U (productnumber)) was used to observe the transdermal absorption sheet 1 tomeasure the rate of the FITC fluorescence intensity of the portion ofthe microneedles 10 with respect to the FITC fluorescence intensity ofthe entire transdermal absorption sheet. FITC was contained only in thesecond transdermal absorption material solution 20B for forming theupper layer. The filling rate at which the portion of the microneedles10 was filled with the second transdermal absorption material solution20B could be determined by measuring the rate of the FITC fluorescenceintensity of the portion of the microneedles.

<Measuring Method for the Filling Rate 2>

In a measuring method for the filling rate 2, the portion of themicroneedles of the transdermal absorption sheet 1 was cut off anddissolved in water to obtain a first solution. Moreover, the entiretransdermal absorption sheet 1 except for the portion of themicroneedles was also dissolved in water to obtain a second solution.The weight of the drug (human growth hormone) contained in each of thefirst and second solutions is quantified using Coomassie (Bradford)Protein Assay Kit (manufactured by Thermo Fisher Scientific K.K.). Thefilling rate was determined to be a rate of the drug amount contained inthe portion of the microneedles with respect to the total drug amount.The measuring method for the filling rate 2 enabled direct evaluation ofhow the drug was successfully concentrated at the microneedles 10.

(Evaluation Criteria for the Filling Rate)

-   -   Rank A . . . 80% or more of the drug was concentrated at the        microneedles. Very good.    -   Rank B . . . 60% or more and 80% or less of the drug was        concentrated at the microneedles. Good.    -   Rank C . . . Only 50% or more and 60% or less of the drug was        concentrated at the microneedles. Bad.    -   Rank D . . . Only less than 50% of the drug was concentrated at        the microneedles. Very bad.

Rank B and higher were defined to be above an acceptance line.

(Results of Test 1)

A table in FIG. 13 depicts the results of tests on Examples 1 to 9 andComparative Examples 1 and 2. Numerical values of the filling rate inFIG. 13 were obtained using the measuring method for the filling rate 1,but the results of the evaluation method 2 are similar to the results ofthe evaluation method 1.

As seen in the table in FIG. 13, in Examples 1 to 9 that use themanufacturing method for the transdermal absorption sheet 1 in thepresent invention, the filling rate was 62% or more. In particular, inExamples 1, 2, and 5 to 9 that meet the conditions that: the upper layerhas a viscosity of 2 to 10 Pa·s; the lower layer has a viscosity of atleast 200 Pa·s; and the viscosity of the lower layer is at least 20times higher than the viscosity of the upper layer, the filling rate was80% or more. This indicates that the drug very favorably concentrated atthe microneedles 10.

On the other hand, for the transdermal absorption sheet in which thelower layer and the upper layer had the same viscosity as in ComparativeExample 1, the filling rate was 51%. This indicates that approximatelyhalf of the drug used was present in the areas other than themicroneedles 10. Furthermore, for the transdermal absorption sheet inwhich the upper layer had a higher viscosity than the lower layer as inComparative Example 2, the filling rate was 20%. This indicates thatmost of the drug failed to concentrate at the portion of themicroneedles.

The above-described comparative results between the examples and thecomparative examples indicate that the present invention allows the drugto concentrate at the microneedles 10 (needle-like protruding portions).Moreover, the viscosity of the upper layer is lower than the viscosityof lower layer so that the upper layer easily enter the needle-likerecessed portion.

[Test 2]

In Test 2, the transdermal absorption sheet 1 was produced using aninfluenza vaccine (influenza HA vaccine manufactured by DENKA SEIKENCo., Ltd.) as a drug, and the drug amount concentrated at the portion ofthe microneedles was checked.

That is, a mixed water solution with a hydroxyethyl starch concentrationof 39 wt % and a sodium hyaluronate concentration of 1 wt % was appliedonto the support 2 to a thickness of approximately 300 μm, and dried at35° C. and at a relative humidity of 40% to form the lower layer. Amixed solution was prepared by adding the influenza vaccine as a drug toa water solution with a hydroxyethyl starch concentration of 14 wt % soas to have a influenza vaccine concentration of 0.1 wt %. Subsequently,the upper layer was formed by coating the surface of the lower layerwith the prepared mixed solution to a thickness of 110 μm. Thus, thetwo-layer film 20 was formed on the support 2. The viscosity of thelower layer produced as described above was 1,000 Pa·s. The viscosity ofthe upper layer produced as described above was 2 Pa·s. The lower layerhad a viscosity 500 times higher than the viscosity of the upper layer.The other conditions under which the transdermal absorption sheet 1 ismanufactured were similar to the conditions in Test 1.

Then, the influenza vaccine contained in the portion of the microneedleswas quantified as follows. That is, the portion of the microneedles wascut off and dissolved in water to obtain a solution. Then, a weight ofthe influenza vaccine contained in the resultant solution was quantifiedusing the Coomassie (Bradford) Protein Assay Kit. As a result of thequantification, the weight of the influenza vaccine in the portion ofthe microneedles was 1.4 μg, which was 83% of an influenza vaccineweight of 1.7 μg contained in the whole transdermal absorption sheet.

The results of Test 2 indicate that implementation of the manufacturingmethod for the transdermal absorption sheet in the present inventionallows a filling rate of 83% to be achieved to concentrate the drug atthe portion of the microneedles even when the influenza vaccine is usedas the drug.

In Test 2, the drug amount was directly measured using theabove-described <Measuring Method for the Filling Rate 2>. When the<Measuring Method for the Filling Rate 1> was used for the measurement,the filling rate was 82%, that is, similar results were obtained.

[Test 3]

Test 3 is a case where the present invention was carried out using atype of transdermal absorption material different from the transdermalabsorption material used in Test 1.

That is, a mixed water solution with a dextran (manufactured by MeitoSangyo Co., Ltd., dextran 70) concentration of 39 wt % and a sodiumhyaluronate concentration of 1 wt % was applied onto the support 2 to athickness of approximately 300 μm, and dried at 35° C. and at a relativehumidity of 40% to form the lower layer. A mixed solution was preparedby adding human growth hormone as a drug and FITC to a water solutionwith a dextran concentration of 14 wt %, so as to have a human growthhormone concentration of 0.25 wt % and an FITC concentration of 0.001 wt%. Subsequently, the upper layer was formed by coating the surface ofthe lower layer with the prepared mixed solution to a thickness of 110μm. The viscosity of the lower layer produced as described above was1,000 Pa·s. The viscosity of the upper layer produced as described abovewas 1 Pa·s. The lower layer had a viscosity 1,000 times higher than theviscosity of the upper layer. As to the other conditions, thetransdermal absorption sheet 1 was produced under conditions similar tothe conditions in Test 1.

The filling rate of the transdermal absorption sheet 1 produced asdescribed above was evaluated in a manner similar to the manner inTest 1. The result was 82% which was a good result.

The results of Test 3 indicate that implementation of the manufacturingmethod for the transdermal absorption sheet in the present inventionallows a filling rate of 82% to be achieved to concentrate the drug atthe portion of the microneedles even when the type of the transdermalabsorption material is changed.

[Test 4]

In Test 4, the transdermal absorption sheet 1 was produced using insulin(manufactured by PEPTIDE INSTITUTE, INC.; human insulin) as a drug, andthe drug amount concentrated at the portion of the microneedles waschecked.

That is, a mixed water solution with a hydroxyethyl starch concentrationof 48.8 wt % and a sodium hyaluronate concentration of 1.2 wt % wasapplied onto the support 2 to a thickness of approximately 240 μm toform the lower layer. A mixed solution was prepared by adding insulin asa drug and FITC to a water solution with a hydroxyethyl starchconcentration of 50 wt %, so as to have an insulin concentration of 0.25wt % and an FITC concentration of 0.001 wt %. Subsequently, the upperlayer was formed by coating the surface of the lower layer that had notbeen dried with the prepared mixed solution to a thickness of 15 μm.Thus, the two-layer film 20 was formed on the support 2. The viscosityof the lower layer produced as described above was 1,000 Pa·s. Theviscosity of the upper layer produced as described above was 2 Pa·s. Thelower layer had a viscosity 500 times higher than the viscosity of theupper layer.

Then, insulin contained in the portion of the microneedles wasquantified as follows. That is, the portion of the microneedles was cutoff and dissolved in water to obtain a solution. Then, a weight ofinsulin contained in the resultant solution was quantified using acommercially available Insulin Human ELISA kit. As a result of thequantification, the weight of insulin in the portion of the microneedleswas 0.48 μg, which was 82% of an insulin weight of 0.58 μg contained inthe whole transdermal absorption sheet.

The results of Test 4 indicate that implementation of the manufacturingmethod for the transdermal absorption sheet in the present inventionallows a filling rate of 82% to be achieved to concentrate the drug atthe portion of the microneedles even when insulin is used as the drug.

In Test 4, the drug amount was directly measured using theabove-described measuring method for the filling rate. When the<Measuring Method for the Filling Rate 1> was used for the measurement,the filling rate was 82%, that is, similar results were obtained.

[Test 5]

In Test 5, the transdermal absorption sheet 1 was produced usingbisphosphonate (manufactured by Wako Pure Chemical Industries, Ltd.;sodium risedronate) as a drug, and the drug amount concentrated at theportion of the microneedles was checked.

That is, a mixed water solution with a hydroxyethyl starch concentrationof 39 wt % and a sodium hyaluronate concentration of 1 wt % was appliedonto the support 2 to a thickness of approximately 300 μm, and dried at35° C. and at a relative humidity of 40% to form the lower layer. Amixed solution was prepared by adding bisphosphonate as a drug to awater solution with a hydroxyethyl starch concentration of 14 wt %, soas to have a bisphosphonate concentration of 0.1 wt %. Subsequently, theprepared mixed solution was applied onto the lower layer to a thicknessof 110 μm, and then dried at 35° C. and at a relative humidity of 40% toform the upper layer. Subsequently, water was applied onto the upperlayer for humidification so as to have a thickness of 100 μm. Thus, thetwo-layer film 20 was formed on the support 2. The viscosity of thelower layer produced as described above was 1,000 Pa·s. The viscosity ofthe upper layer produced as described above was 2 Pa·s. The lower layerhad a viscosity 500 times higher than the viscosity of the upper layer.

Then, the bisphosphonate contained in the portion of the microneedleswas quantified as follows. That is, the portion of the microneedles wascut off and dissolved in water to obtain a solution. Then, a weight ofthe bisphosphonate contained in the resultant solution was quantifiedusing LC-MS. As a result of the quantification, the weight of thebisphosphonate in the portion of the microneedles was 0.48 μg, which was82% of a bisphosphonate weight of 0.58 μg contained in the wholetransdermal absorption sheet.

The results of Test 5 indicate that implementation of the manufacturingmethod for the transdermal absorption sheet in the present inventionallows a filling rate of 82% to be achieved to concentrate the drug atthe portion of the microneedles even when the bisphosphonate is used asthe drug.

In Test 5, the drug amount was directly measured using theabove-described measuring method for the filling rate. When the<Measuring Method for the Filling Rate 1> was used for the measurement,the filling rate was 82%, that is, similar results were obtained.

[Test 6]

In Test 6, the present invention was carried out using a transdermalabsorption material with a three-layer configuration of a lower layer,an intermediate layer, and an upper layer.

That is, a mixed water solution with a hydroxyethyl starch concentrationof 39 wt % and a sodium hyaluronate concentration of 1 wt % was appliedonto the support 2 to a thickness of approximately 260 μm, and dried at35° C. and at a relative humidity of 40% to form the lower layer.Subsequently, a water solution with a hydroxyethyl starch concentrationof 40 wt % was applied onto the lower layer to a thickness ofapproximately 40 μm, and dried at 35° C. and at a relative humidity of40% to form the intermediate layer. A mixed solution was prepared byadding human growth hormone as a drug and FITC to a water solution witha hydroxyethyl starch concentration of 14 wt %, so as to have a humangrowth hormone concentration of 0.25 wt % and an FITC concentration of0.001 wt %. Subsequently, the upper layer was formed by coating thesurface of the intermediate layer with the prepared mixed solution so asto have a thickness of 110 μm, The viscosity of the lower layer producedas described above was 1,000 Pa·s. The viscosity of the intermediatelayer produced as described above was 2 Pa·s. The viscosity of the upperlayer produced as described above was 2 Pa·s. The viscosity differencebetween the lower layer and the upper layer corresponded to 500 times.As to the other conditions, the transdermal absorption sheet wasproduced under the conditions similar to Test 1.

The filling rate of the transdermal absorption sheet produced asdescribed above was evaluated in a manner similar to the manner inTest 1. The result was 82% and was a good result.

The results of Test 6 indicate that implementation of the manufacturingmethod for the transdermal absorption sheet in the present inventionallows a filling rate of 82% to be achieved to concentrate the drug atthe portion of the microneedles even when the three-layer configurationis used as the transdermal absorption sheet material.

What is claimed is:
 1. A transdermal absorption sheet in which aplurality of fine needle-like protruding portions are arranged in atwo-dimensional array on a surface of a sheet portion supported by asupport, wherein a tip of each of the needle-like protruding portionscontains a drug and hydroxyethyl starch, and a base of each of theneedle-like protruding portions contains hydroxyethyl starch andhyaluronic acid.
 2. A transdermal absorption sheet in which a pluralityof fine needle-like protruding portions are arranged in atwo-dimensional array on a surface of a sheet portion supported by asupport, wherein a tip of each of the needle-like protruding portionscontains a drug and chondroitin sulfate, and a base of each of theneedle-like protruding portions contains hydroxyethyl starch.